TITLE: 1961-90 MEAN MONTHLY PRECIPITATION MAPS FOR THE CONTERMINOUS UNITED STATES

AUTHORS: Christopher Daly and George Taylor, with the Oregon Climate Service

DATE OF DOCUMENTATION:  20 August 1998

DESCRIPTION:
 
These final mean monthly precipitation estimates were generated by Christopher Daly 
using the PRISM model (Daly et al. 1994, Daly et al. 1997). Data input to the model 
consisted of 1961-90 mean monthly precipitation from over 8000 NOAA Cooperative sites, 
SNOTEL sites, and selected state network stations.  Data-sparse areas were supplemented 
by a total of about 500 shorter-term stations. A station was included in this data set 
if it had at least 20 years of valid data, regardless of its period of record. Each monthly 
map was made by patching together individual state maps for the 11 western states, a central
US region, an eastern US region, and a New England region. PRISM software was used to 
minimize "seams" along state and region boundaries. 
 
The annual maps were created by summing the 12 monthly maps.  The annual maps underwent 
extensive peer-review by many state climatologists and other experts. This is part of a 
national effort by the USDA Natural Resources Conservation Service and Oregon State 
University to develop state-of-the-art precipitation maps for each state in the US, 
including Alaska and Hawaii.
 

REFERENCES:
 
When referring to this data set, please cite the following papers:
 
Daly, C., R.P. Neilson, and D.L. Phillips.  1994.  A statistical-topographic model for
mapping climatological precipitation over mountainous terrain. Journal of Applied 
Meteorology 33: 140-158.  

Daly, C., G.H. Taylor, and W.P. Gibson.  1997.  The PRISM approach to mapping precipitation 
and temperature, In reprints: 10th Conf. on Applied Climatology, Reno, NV, American 
Meteorological Society, 10-12.  
  

GRID DIMENSIONS, PROJECTION, RESOLUTION, UNITS AND FORMAT:
 
See correspoding metadata file.
  

CONTACTS:
 
See Contacts link on the PRISM Web page.